Fatigue characteristics of high strength C70S6 and SMA40 steels

In this study, fatigue characteristics of C70S6 and SMA40 materials as a potential application in connecting rod for an Internal Combustion (IC) engine were investigated. An average fatigue life of 140,200 and 168,700 cycles and a fatigue limit of 432 and 437 MPa were determined for C70S6 and SMA40 specimens, respectively. However, when tested under the fretting condition, the fatigue lifetime was decreased by 77.8% and 20% and the fatigue limit was reduced to 96 and 350 MPa for C70S6 and SMA40 specimens, respectively. From the observations of fracture surfaces, it was confirmed that the fretting played a critical role in introducing many cracks at the initial stage of fatigue. It is clearly shown in this study that special attention should be given to the fatigue behavior of given materials under fretting condition to ensure reliable design and application of components in an automobile.